Write out the output expression of the following circuit(Fig 1) and draw the output waveform according to known input waveform(Fig 2)(8 points). B U4A USA 74LS08J 74LS040 U12A U1A 14 USB 74L$32D 74LS08J 74LS04D U2A 74LS08 Fig 1 (1) Write the output expression of the following circuit(4 points ). (2) Draw the output waveform according to input waveform in Fig 2(4 points)